The present invention relates generally to the plastic card manufacturing industry and, more specifically, to the manufacture of dual-interface smart cards.
Smart cards are well known devices that include a plastic card body into which is embedded an integrated circuit (IC). The integrated circuit is designed to store data that can be used, inter alia, to provide the card with electronic identification, authentication, data storage and application processing capabilities. As a result, smart cards are widely used in commerce to provide information and/or application processing capabilities in connection with, but not limited to, bank cards, credit cards, health insurance cards, driver's licenses, transportation cards, loyalty cards and membership cards.
The card body for a smart card is typically constructed out of one or more layers of any durable plastic material, such as polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS) or polycarbonate. The dimensions of the card body are typically similar to the dimensions of a conventional credit card (i.e., 3.370 inches in length, 2.125 inches in width and 0.030 inches in thickness).
The integrated circuit (IC) is typically constructed as part of an integrated circuit (IC) module that includes a lead frame having a bottom surface on which the integrated circuit is fixedly mounted using a chip adhesive. The exposed portion of the IC is in turn encapsulated within a hard epoxy resin for protective purposes. As part of the smart card manufacturing process, the IC module is mounted, chip side down, into a fitted recess that is milled or otherwise formed into the top surface of the card body and is fixedly held in place using a hot melt adhesive.
Smart cards of the type as described above transmit data stored on the integrated circuit using either (i) a direct contact interface (the resultant products being commonly referred to in the art as contact smart cards), (ii) a contact-free interface (the resultant products being commonly referred to in the art as contactless smart cards) or (iii) a hybrid of the two aforementioned interfaces (the resultant products being commonly referred to in the art as dual-interface smart cards).
The contact interface for a dual-interface smart card is typically constructed as a plurality of gold-plated contact pads that are fixedly mounted onto the top surface of the lead frame and are arranged to form a total contact surface area of approximately 1 square centimeter. The underside of each contact pad is individually electrically connected to the integrated circuit by a corresponding gold-plated wire, the wires being encapsulated by a hard epoxy resin for protective purposes. As such, it is to be understood that the contact pads serve as an electrical interface for the IC when the smart card is inserted into an appropriate reader.
The contact-free interface for a dual-interface smart card is typically provided by a conductive antenna that is incorporated into the card body by any suitable means, such as through the use of embedding, etching, plating, printing or the like. Preferably, the antenna is arranged in a coiled, or spiraled, configuration around the IC module cavity and is, in turn, electrically connected to the integrated circuit, as will be described further in detail below. Accordingly, in response to an interrogation signal, information stored on the integrated circuit can be transmitted by the antenna as a radio frequency (RF) signal.
As noted above, the integrated circuit for a dual-interface smart card must be electrically connected to the antenna to effectively transmit data. Typically, a pair of opposing metal contact pads are mounted onto the underside of the lead frame, each contact pad being individually electrically connected to the integrated circuit by a corresponding gold-plated wire which is then encapsulated within a hard epoxy resin for protective purposes. The card body is then drilled, or routed, to the extent necessary so that the conductive component of the antenna is externally exposed at two separate locations.
Various techniques are known in the art for electrically connecting each contact pad formed on the underside of the IC module with a corresponding exposed portion of the antenna.
One such technique involves overfilling each routed hole with a conductive epoxy material that creates a convex protrusion or bump in direct alignment with each of the contact pads formed on the underside of the IC module. Accordingly, when the IC module is permanently affixed to the card body, an electrical connection is established between the integrated circuit and the antenna through the conductive epoxy.
The above-described method for electrically connecting the IC module to the antenna has been found in the industry to be largely unsatisfactory. Specifically, the conductive epoxy has been found to fragment, crack or otherwise break at one or both of its connection points in response to torsion or stress applied to the smart card during use and/or testing. As a result of the electrical disconnection of the IC module from the antenna, the smart card loses its RF signal transmission capabilities, which is highly undesirable.
In response, a number of alternative approaches for electrically connecting the IC module to the antenna have been implemented in the smart card manufacturing industry. However, these alternative approaches have been found to similarly suffer from a number of notable shortcomings including: (i) being considerably labor-intensive and time-consuming in nature, (ii) requiring the purchase of additional manufacturing equipment, and/or (iii) utilizing glues with limited shelf time.
Accordingly, it is an object of the present invention to provide a relatively inexpensive smart card that is flexible enough to support some stress but, at the same time, has the requisite structural integrity to maintain a strong physical connection of the IC module to the antenna.